(1) Field of the Invention
This invention relates to an electromagnetic imaging apparatus for use in the medical and industrial fields to detect electromagnetic waves such as light and other radiation, and to a method of manufacturing such apparatus. More particularly, the invention relates to a technique for depositing and joining a detector panel for detecting electromagnetic radiation and a readout panel for reading, from the detector panel, carriers which are electron-hole pairs generated as a result of detection of the electromagnetic radiation.
(2) Description of the Related Art
A construction of a conventional electromagnetic imaging apparatus will be described with reference to FIGS. 1 and 2.
FIG. 1 is a sectional view showing a detector panel for detecting electromagnetic radiation. FIG. 2 is a sectional view of the detector panel and a readout panel joined together. For expediency of illustration, FIG. 1 shows only a fragment corresponding to three pixels, and FIG. 2 only a fragment corresponding to one pixel.
As shown in FIG. 1, a detector panel 10 of a conventional electromagnetic imaging apparatus has a bias application electrode 12 formed on a substantially entire surface of a supporting substrate 11. Deposited on this bias application electrode 12 (on its under surface in FIG. 1) is a converter layer 13 for generating carriers, which are electron-hole pairs, as a result of detecting electromagnetic radiation. Numerous pixel electrodes 14 are formed on this converter layer 13. In order to promote the rate of collecting the carriers (hereinafter referred to as “charges” also) from the detector panel 10 for an improved readout response, and also to prevent interpixel crosstalk (hereinafter just “crosstalk” where appropriate) of the carriers, it is believed desirable to set a low resistance to the connection between the detector panel 10 and a readout panel 20 to be described hereinafter. Thus, a metallic material is used for the pixel electrodes 14.
As shown in FIG. 2, the readout panel 20 of the conventional electromagnetic imaging apparatus is in the form of an active matrix panel including an insulating substrate 21 having electrode lines 22 arranged in a lattice or crisscross pattern thereon, a plurality of switching elements 23 provided one for each lattice section, a plurality of reading electrodes 24 connected to the electrode lines 22 through the switching elements 23, and a plurality of charge collecting stores 25 electrically connected to the reading electrodes 24. The readout panel 20 will be called the active matrix panel in the following description.
The detector panel 10 and active matrix panel 20 are connected together through an electroconductive resin 30 disposed between each pair of pixel electrode 14 and reading electrode 24.
According to the conventional electromagnetic imaging apparatus having the above construction, incident radiation generates charges in the converter layer 13 of detector panel 10. These charges are transmitted through the pixel electrodes 14, electroconductive resin 30 and reading electrodes 24 to the charge collecting stores 25 to accumulate therein. The charges collected in the charge collecting stores 25 are read through the switching elements 23 turned on.
The above conventional construction has the following drawbacks.
In order to form the minute pixel electrodes 14 on the converter layer 13 of detector panel 10 by photolithography, the surface of converter layer 13 must be made a flat surface of 1 micron or less, for example. The converter layer 13 is formed in a relatively large thickness. As a result, its thickness tends to vary, making it difficult to level out the surface over large areas.
In addition, formation of the pixel electrodes 14 requires various devices such as a pattern forming mask, an exposing device and an etching device.
Further, a high degree of precision is required in adjusting a relative position between the pixel electrodes 14 of detector panel 10 and the reading electrodes 24 of active matrix panel 20, which complicates the manufacturing process.